CODEWITHSUNDEEP
objective-cios
AppleGuy
AppleGuy

Reputation: 3

Can't Shorten NSString Length

I am trying to make this program so that the only time that there is a decimal is when the decimal is .5. I have been trying to use [string substringToIndex:[string length] - 2] but it does nothing. Is is because it cannot append the float?

float inchesInField = [sizeField.text floatValue];
float shoeSize = inchesInField * 3 - 22;
NSMutableString *appendedShoeSize = [[NSMutableString alloc]
                                            initWithFormat:@"%.1f", shoeSize];

if ([appendedShoeSize hasSuffix:@".3"] || [appendedShoeSize hasSuffix:@".5"] ||
    [appendedShoeSize hasSuffix:@".4"] || [appendedShoeSize hasSuffix:@".6"])
{
    [appendedShoeSize substringToIndex:[appendedShoeSize length] - 2];
    [appendedShoeSize appendString:@" ½"];
} 

if ([appendedShoeSize hasSuffix:@".0"] || [appendedShoeSize hasSuffix:@".1"] ||
    [appendedShoeSize hasSuffix:@".2"])
{
    [appendedShoeSize substringToIndex:[appendedShoeSize length] - 2];
}

Upvotes: 0

Views: 689

Answers (4)

CRD
CRD

Reputation: 53000

This isn't an answer but an alternative, all those hasSuffix:'s just grated a bit. I think this does what you want:

float intpart;
float fracpart = modff(shoeSize, &intpart);
NSMutableString *appendedShoeSize;

int size = (int)intpart;
if (fracpart >= 0.3 && fracpart <= 0.6)
    appendedShoeSize = [[NSMutableString alloc] initWithFormat:@"%d½", size];
else
{   if (fracpart > 0.6) size += 1;
    appendedShoeSize = [[NSMutableString alloc] initWithFormat:@"%d", size];
}

modff splits a float into its fractional (return value) and integer (via reference argument) parts. This code fragment doesn't require a mutable string, but I left that in as you might be doing other things with it later. The fragment also bumps .7 -> .9 to the next size.

Upvotes: 0

Daniel
Daniel

Reputation: 23359

it is because substringToIndex: method of NSString returns the new string, it doesn't modify the original string. appendString: is fine, but substringToIndex: is a method of NSString so it will not edit the original string.

This should do it:

float inchesInField = [sizeField.text floatValue];
float shoeSize = inchesInField * 3 - 22;
NSMutableString *appendedShoeSize = [[NSMutableString alloc] initWithFormat:@"%.1f", shoeSize];

if ([appendedShoeSize hasSuffix:@".3"] || [appendedShoeSize hasSuffix:@".5"] || [appendedShoeSize hasSuffix:@".4"] || [appendedShoeSize hasSuffix:@".6"]) {

    appendedShoeSize = [[appendedShoeSize substringToIndex:[appendedShoeSize length] - 2] mutableCopy];
    [appendedShoeSize appendString:@" ½"];
} 

if ([appendedShoeSize hasSuffix:@".0"] || [appendedShoeSize hasSuffix:@".1"] || [appendedShoeSize hasSuffix:@".2"]) {

    appendedShoeSize = [[appendedShoeSize substringToIndex:[appendedShoeSize length] - 2] mutableCopy];
}

Upvotes: 3

seppo0010
seppo0010

Reputation: 15849

As Daniel pointed out substringToIndex: returns a new string.

You should use replaceCharactersInRange:withString:, for example:

NSRange range; range.location = [appendedShoeSize length] - 2; range.length = 2;
[appendedShoeSize replaceCharactersInRange:range withString:@" ½"]

More reference about NSMutableString methods can be found at http://developer.apple.com/library/mac/#documentation/Cocoa/Reference/Foundation/Classes/NSMutableString_Class/Reference/Reference.html

Upvotes: 0

arnaud del.
arnaud del.

Reputation: 912

When you call substringToIndex:, it won't modify the existing string. It returns a result. You have to use something like : NSString * result = [appendedShoeSize substringToIndex:[appendedShoeSize length] - 2];

Upvotes: 0

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